Aluminum-iron powder mixture for powder lancing



United States Patent 4 Claims. (Cl. 75-.5)

This invention relates to powder lancing of refractory material from a body thereof, and more particularly, to an improved aluminum-iron powder mixture for use in such powder lancing operations.

It is well known in the art that the addition of aluminum to a powdered metallic fuel for use in thermochemical metal removal processes reduces the preheating time required and considerably increases the rate of metal removal. Therefore, from an economics standpoint, the addition of aluminum to such powder has assumed great commercial importance. However, because of its high flashing potential and its tendency to segregate out from the rest of the powdered metallic fuel mixture, particularly during shipment, the addition of aluminum to such powdered fuels has increased the potential hazards to operating personnel performing the various powder processes.

Heretofore particularly in powder lancing applications, it has been the practice for the user to mix his own aluminum-iron powdered fuel. Even when the recommended rates of aluminum to iron, not over 30% aluminum, were used in such mixes, the use of both aluminum and iron powder particles of random screen size, and incomplete mixing and blending of the two elements, often resulted in a powdered fuel imminently susceptible to flashing, both in the lancing tool itself and in its path of travel to the lance, with consequent injury to the operator as well as damage to the equipment. In addition, the segregation which resulted from such on-site mixing, besides being a safety hazard, undesirably interfered with the smooth burning reaction during the lancing operations.

Therefore, it is the object of this invention to provide a premixed aluminum-iron powdered fuel for powder lancing applications consisting of from 15 to 30% aluminum wherein the particles sizes of both constituents are so controlled as to preclude the possibility of segregation of one element from the other, wherein the tendency of the powder to flash or pre-ignite has been eliminated or reduced to an absolute minimum, and wherein the process efliciency has not been decreased thereby.

According to the invention, it has been found that in addition to an initial complete and intimate mixing and blending of the elements, certain factors are essential in the production of such a premixed aluminum-iron powder mixture as outlined above. These factors are:

Ratio of aluminum to iron should not exceed 30%.

Of this percentage of aluminum, less than 3% should be of -325 mesh particle size or under.

Of the iron powder, 20% or less should be of -325 mesh particle size.

A certain relationship of the percentages of the various particle sizes between the two elements should be maintained. For example, the following ranges of percentages of various particle sizes for the aluminum and iron mixture have been found to be the most effective for preventing segregation and pre-ignition:

Iron Powder, to Aluminum Powder, 30 to 15% Percent Percent On 60 mesh .01 Through 30 mesh On 100 mesh 16 to 23 On 60 mesh 16 to 23 On 200n1esh 30 to 40 On 100 mesh On 325 mesh 20m 30 On 200 mesh 325 mesh 20 or less 200 mesh If this relationship of the dispersion of particle sizes of the two elements is deviated from to too great an extent, for instance, the on 200 mesh size particles of aluminum increased to 40% and this combined with iron powder containing predominantly larger size particles such as 40% on 100 mesh, the tendency of the two elements to segregate would be markedly increased as well as its tendency to pre-ignite. In order to prevent segregation and pre-ignition, a more equal dispersion over the particle size range of the two powders must be maintained as indicated by the above ranges.

The upper particle size limit is dictated by the necessity of taking into account the powder dispensing apparatus. Powder which contains particles larger than those cited above tend to interfere with the required smooth, even feeding of the powder from the dispenser to the lancing tool. The lower particle size limits are dictated by the desire to prevent segregation and pre-ignition or flashing of the powder. The more fines there are present in the powder mixture, the greater the tendency for fines to segregate out and cause the powder to flash.

An example of a pre-mixed aluminum and iron powder mixture which has been found to combine the desired ease of dispensing and freedom from segregation and susceptibility to flashing with the required lancing efficiency is as follows:

Iron Powder. 85% Aluminum Powder, 15%

The pre-mixed aluminum-iron powder of the invention provides the advantages of increased safety, better flow characteristics due to the larger particle size, eliminating segregation during shipment, eliminating expensive job site proportioning and mixing, and eliminating possibility of the powder picking up contaminants such as moisture and foreign trash during such job site mixing.

This applicaiton is a continuation of my copending application Serial No. 3,711, filed January 21, 1960.

What is claimed is:

l. A premixed fiowable oxidizing gas lancing powder mixture consisting essentially of between 70 and 85% by weight iron powder and the remainder aluminum powder, the proportions by weight of particle sizes being of:

Iron on 100 mesh from 16 to 23%, on 200 mesh from 30 to 40%, and on 325 mesh from 20 to 30% with less than 20% passing 325 mesh; and of Aluminum on 60 mesh from 16 to 23%, on 100 mesh from 53% to 63%, and on 200 mesh from 15 to 25% with less than 3% passing 325 mesh;

To avoid segregation between the aluminum and iron particles and to avoid flashback of the finest particles.

2. A premixed flowable oxidizing gas lancing powder mixture consistiing essentially of by weight between 70 and 85% iron powder and the remainder aluminum powder, the proportions by weight of particle sizes being approximately:

Iron, on 100 mesh 17%, on 200 mesh 37%, on 325 mesh 26% with less than 20% passing 325 mesh; and of Aluminum, on 60 mesh 18%, on 100 mesh 54%, on 200 mesh 24% with less than 3% passing 325 mesh;

Whereby segregation between the iron and aluminum particles and flashback of fine particles are preeluded.

3. In the method of powder lancing, the improvement which comprises introducing into the oxidizing gas stream a premixed lancing powder mixture of between 70 and 85% by weight iron powder and the remainder aluminum powder, the proportions by weight of particle sizes being of:

Iron on 100 mesh 16 to 23%, on 200 mesh from to and on 325 mesh from 20 to 30% with less than 20% passing 325 mesh, and of Aluminum on mesh 16 to 23%, on 100 mesh from 53 to 63%, and on 200 mesh from 15 to 25% with less than 3% passing 325 mesh,

To avoid segregation between the aluminum and iron particles and to avoid flashback of the finest particles.

4. In the method of powder lancing, the improvement which comprises introducing into the oxidizing gas stream a premixed lancing powder mixture of between and by weight iron powder and the remainder aluminum powder, the proportions by weight of particle sizes being approximately:

Iron, on mesh 17%, on 200 mesh 37%, on 325 mesh 26% with less than 20% passing 325 mesh; and of Aluminum, on 60 mesh 18%, on 100 mesh 54%, on 200 mesh 24% with less than 3% passing 325 mesh;

Whereby segregation between the iron and aluminum particles and flashback of fine particles are precluded.

References Cited in the file of this patent UNITED STATES PATENTS 2,916,373 Freeman Dec. 8, 1959 

1. A PREMIXED FLOWABLE OXIDIZING GAS LANCING POWDER MIXTURE CONSISTING ESSENTIALLY OF BETWEEN 70 AND 85% BY WEIGHT IRON POWDER AND THE REMAINDER ALUMINUM POWDER, THE PROPORTIONS BY WEIGHT OF PARTICLE SIZES BEING OF: IRON ON 100 MESH FROM 16 TO 23%, ON 200 MESH FROM 30 TO 40%, AND ON 325 MESH FROM 20 TO 30% WITH LESS THAN 20% PASSING 325 MESH; AND OF ALUMINUM ON 60 MESH FROM 16 TO 23%, ON 100 MESH FROM 53% TO 63%, AND ON 200 MESH FROM 15 TO 25% WITH LESS THAN 3% PASSING 325 MESH; TO AVOID SEGREGATION BETWEEN THE ALUMINUM AND IRON PARTICLES AND TO AVOID FLASHBACK OF THE FINEST PARTICLES. 